Yama said: "Though thou hadst seen the fulfilment of all desires, the foundation of the world, the endless rewards of good deeds, the shore where there is no fear, that which is magnified by praise, the wide abode, the rest, yet being wise thou hast with firm resolve dismissed it all.

In plain words: Yama says Nachiketas was shown every wish come true, great rewards, a place without fear, and lasting rest. Yet, being wise, he firmly put all of it aside.